1. Field of the Invention
The embodiments described herein relate generally to imaging methods and systems and, more particularly, to imaging methods and systems that use Compton scatter to generate an image.
2. Description of Related Art
During at least some imaging scans using X-rays, a portion of the X-rays are absorbed by an object, another portion of the X-rays are transmitted through the object, and yet another portion of the X-rays are scattered by the object. Back scattering of photons from the object is referred to herein as “Compton scatter,” “Compton back scatter,” “back scatter,” or “reflected inelastic scatter.” In at least some known X-ray systems, Compton scatter is used for imaging superficial regions of extended volumes by measuring an intensity of the Compton scatter. The intensity of Compton scattering depends on local electron density, which is similar to the physical density for materials composed of light elements, and can be used to generate images of the scanned object. However, such Compton scatter imaging measures a total reflected X-ray signal without regard to energies of back scattered photons.
At least some known inspection tasks benefit from the capability to differentiate between substances based on their chemical properties. Such a capability is also referred to as molecular specific imaging. One known type of molecular specific imaging is X-ray diffraction imaging, in which Bragg peaks are analyzed to give information on crystal lattice spacings. Bragg peaks are generated using forward coherent scattered photons rather than back scattered inelastic photons. As such, back scattered photons are currently used for electron density imaging, and forward scatter photons are used for molecular specific imaging. Although Compton back scatter is used for intensity imaging, it is desirable to also use Compton back scatter for molecular specific imaging and/or identification.